Conventional ball valves may include a spherical or semispherical shaped sealing member within a liquid flow passage. The sealing member may include a central opening through which liquid may flow depending on the orientation of the sealing member within the flow passage. To prevent liquid flow about the sealing member, seals may be providing along inner walls of the flow passage which engage an outer portion of the sealing member. Typically, a seal is provided on each of the upstream and downstream sides of the valve and the seals are spaced apart wider than the width of the central opening through the sealing member.
When open, the central passage of the sealing member of a conventional ball valve is generally oriented parallel to an axis of flow through the flow passage. As a conventional ball valve is closed, the central opening of the sealing member is rotated away from alignment with the axis of the flow passage. When fully closed, the central opening of the sealing member will typically still contain a certain amount of the liquid. This liquid is held within the central opening by the same seals that prevent flow of liquid about the sealing member.
The fluid held within the central passage of a closed ball valve may be begin to deteriorate or to stagnate. When the valve is reopened, the degraded fluid with the central passage may enter the fluid delivery system downstream of the valve and may contaminate the liquid being delivered.
Other conventional valve types may also include pockets or recesses where liquid being transported through the valve may become trapped.
It is desirable to improve on valves used in liquid delivery systems.
In stadiums and other large facilities that may have a number of concession stands spread out over a large area, it is common to centralize the liquid supply for beer, soda and other drinks that may be dispensed at the concession stands or other points of purchase. Liquid delivery networks are provided to transport liquid from the central supplies to each concession stand. It is not uncommon for delivery lines to extend for four hundred to eight hundred or more feet. In such installations, it is desirable to have a sensor at the supply end of the line to shut off flow into the line when a soda container or beer keg has been depleted and gas starts to enter the line. If the gas is permitted to run the length of the supply line to the tap, it can take an undesirable amount of time to refill the lines after the soda or beer has been replaced.
Self-closing control valves for use with such installations are known. An example of such a liquid/gas shut-off valve is described in U.S. Pat. No. 5,630,441, the disclosure of which is incorporated herein by reference. However, these self-closing valves require a reset mechanism once the source of beer or soda has been replaced. Different versions of resets have been developed but none is completely satisfactory.
Problems with conventional approaches to resetting these self-closing valves include a lack of robustness and requiring a high degree of precision or care in operation.
Another issue with conventional self-closing valves and reset options is that often these valves and resets also act as check valves. When it is necessary to clean the delivery lines between the source and the tap, bi-directional flow of cleaning solution through the lines may be desired. The check valves used in the self-closing valves and the valve resets may either prevent or hinder the flow of cleaning solution through the delivery lines.
Improvements to resets for self-closing valves and for check valves used in liquid delivery systems are desirable.